(a) Technical Field
The present invention relates to a lithium-air hybrid battery. More particularly, it relates to a lithium-air hybrid battery and a method for manufacturing the same, which has a structure in which a liquid electrolyte electrode and a solid electrolyte electrode are stacked on both sides of an ion conductive glass ceramic.
(b) Background Art
While lithium-ion batteries for hybrid and electric vehicles developed so far satisfy plug-in hybrid electric vehicles (PHEVs) used for short-distance travel, a new energy storage system capable of storing much more energy is required for electric vehicles used for long-distance travel. Among the energy storage systems known so far, a lithium-air battery has a high theoretical capacity. According to the lithium-air battery, during discharge, lithium cations migrate from a lithium metal to a positive electrode through an electrolyte and react with oxygen supplied from the air to produce lithium oxide (such as Li2O or Li2O2). At this time, electrons migrate from a negative electrode to the positive electrode through an electrical circuit.
As shown in FIG. 8, a conventional lithium-air battery typically includes a lithium metal negative electrode 1, an air positive electrode 2, and a separator 3 disposed between the lithium metal negative electrode 1 and the air positive electrode 2, and a liquid electrolyte 4 is included in the lithium metal negative electrode 1 and the air positive electrode 2, respectively.
During discharge of the conventional lithium-air battery, lithium ions (Li+) are deintercalated from the lithium metal negative electrode 1, dissolved in the liquid electrolyte 4, and passed through the separator 3, and then moved to the surface of the air positive electrode 2. On the surface of the air positive electrode 2, the lithium ions react with oxygen supplied from the air to produce lithium oxide and, at this time, charges move from the lithium metal negative electrode 1 to the air positive electrode 2. The separator 3 employed in the conventional lithium-air battery is made of glass fiber or PE-PP material, and both the lithium metal negative electrode 1 and the air positive electrode 2 include the liquid electrolyte 4. As the liquid electrolyte 4, a carbonate solvent having high ion conductivity and low volatility is typically used.
However, the electrolyte of the conventional lithium-air battery contains a volatile solvent, and thus a membrane and a gas diffusion layer (GDL) for preventing volatilization of the electrolyte are provided on the air positive electrode 2 in a position open to the outside. However, the present membranes and GDLs limit the dispersion of oxygen and/or do not inherently prevent the volatilization of the electrolyte, which is very problematic.
Moreover, during the volatilization of the electrolyte, an electrolyte limitation occurs in a battery cell, which shortens the lifespan of the battery, and the moisture in the air passing through the membrane is dissolved in the electrolyte and move to the negative electrode to cause a side reaction with the lithium metal. Further, when a liquid electrolyte is used, the air positive electrode should have an open structure to allow the liquid electrolyte to be in contact with the air, and thus the open position should be fixed (in a direction opposite to gravity). This structure, however, makes it very difficult to employ a stacking structure for increasing the energy density of the battery.
Furthermore, the amount of lithium carbonate (LiCO3) or lithium alkyl carbonate (Li—R—CO3) produced by the decomposition of the electrolyte is much greater than the amount of lithium oxide produced as a discharge product of the air positive electrode in a structure where a carbonate-based liquid electrolyte comes into contact with oxygen, which significantly shortens the lifespan of the lithium-air battery. As such, research on appropriate catalysts and carbon materials used in the air positive electrode of the lithium-air battery is important, but the research on the electrolyte materials is also very important.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.